1. Field of the Invention
The invention relates to combustors and transitions for industrial gas turbines, and more particularly modular drop-in combustors and transitions that are preassembled in conformity with assembly and function specifications prior to installation into an industrial gas turbine. The invention also relates to methods for installation of transitions into an industrial gas turbine.
2. Description of the Prior Art
Known industrial gas turbines utilize replaceable combustors with flanged connections to access ports in the combustor case. In known combustor designs a generally annular-shaped combustor basket has an open tip portion distal the combustor flange that is inserted in nesting fashion into a corresponding inlet end of a combustor transition along an insertion path that is coaxial with the centerlines of the respective access port, combustor basket and transition opening. The transition is inserted prior to the combustor along an insertion path that is also coaxial with the centerline of the respective access port. A known inlet support fixes relative orientation of the transition inlet port and the access port. Thereafter the combustor is inserted into the transition opening. Transition and combustor insertion are often performed sequentially with cranes and/or block and tackle gear to hold their respective weight, in conjunction with human alignment of both along their common coaxial alignment path within the combustor case. The respective combustor and transition lengths are much greater than their respective radial clearance between those assemblies' outer circumferences and other turbine components that are inside or outside the combustor case. A small yaw deviation of the either the transition or combustor assemblies from their respective desired insertion paths may result in inadvertent impact contact between an assembly and another turbine component—possibly resulting in misalignment out of conformance with alignment and function specifications.
In known turbine designs there is insufficient clearance between a fully assembled combustor or transition assembly and other turbine components that are external the combustor case, so it becomes impossible to align and insert a fully assembled combustor. Fully assembled combustor weight of over 1200 pounds (545 kg) further complicates precise combustor alignment during installation, especially if alignment is primarily performed by human operators. Similarly, a fully assembled transition weighs over 242 pounds (110 kg) and typically has a relatively difficult to maneuver length to radial clearance ratio of approximately 5:1. The relatively long and thin transition assembly has to be inserted fully within the combustor case with only slight yaw deviation from its alignment path. For example, during initial insertion of the transition assembly exit end into the combustor access port there is only approximately 0.6 inch (16 mm) total minimum radial clearance between the exit end outer periphery and the access port inner diameter.
Given lack of fully assembled combustor installation clearance and alignment complexities that are exacerbated by combustor weight, the known industry solution is to assemble combustor sub components in situ within the combustor case access port during initial assembly, service and field maintenance and insertion of the combustor. Assembly of sub components within a combustor access port to build a complete combustor and subsequent inspection for conformity with alignment/performance specifications is much slower than factory or authorized service facility bench assembly and inspection. Factory and/or service center pre-assembly in a controlled environment may also be performed by dedicated assembly specialists who may have more practical assembly experience and skills than some field personnel who must perform a broader range of repair services. Unfortunately pre assembly of drop in combustors is not feasible if there is insufficient installation clearance for fully assembled units, or if required installation precision alignment cannot be achieved reliably and consistently in the field due to component gross weight or lack of precise alignment fixtures.
With respect to transition installation known challenges, both the transition inlet mouth and exit mouth simultaneously require precise radial alignment of a relatively axially long tubular structure that is inserted into a blind cavity through an access port. Small tolerences are needed for proper coaxial alignment of the transition inlet to the combustor basket exit mouth require relatively precise co-axial alignment of the transition inlet mouth with the combustor case access port along the insertion/alignment path. Additionally, precise alignment of the transition assembly exit mouth to the gas turbine section inlet face along the insertion path is required. The transition exit must mate with transition seals that are necessary for elimination of air leakage at the transition exit/turbine section inlet interface.
There is a need for industrial gas turbines with sufficient external clearance outside the combustor case that facilitate direct alignment and installation of preassembled transitions into combustor case access ports along an installation path without undue risk of inadvertent transition contact/impact with other turbine components inside or outside the combustor case, that may damage the transition or the other contacted components.
There is also a need for a transition handling tool and transition installation method that facilitate alignment and insertion of heavy pre-assembled relatively long transitions, preferably under automatic control, with repeatable manipulation steps. Ideally such a transition handling tool can remain permanently installed proximal the combustor case access ports for use as needed, or easily transported to and reassembled at various job sites by repair personnel.